1. Technical Field
The invention concerns the production of fabric, and more particularly, the production of non-woven fabric.
2. Discussion of Related Art
The invention concerns on the one hand a forming head for an apparatus for the production of a non-woven fabric and on the other hand a process for processing fibres for the production of a non-woven fabric. The forming head has at least one fibre feed means which opens into a fibre processing chamber. The fibre processing chamber has a deposit opening for the delivery of fibres for example on to a conventional, air-permeable conveyor belt, below which is arranged a so-called suction box. A plurality of needle rollers which engage into each other, with longitudinal axes oriented in mutually parallel relationship, are arranged in the fibre processing chamber. The needle rollers are rotatable about their longitudinal axis.
Accordingly the process includes as process steps the feed of fibres to a forming head and the uniform distribution of the fibres on a conveyor belt by means of the forming head.
Forming heads and processes of that kind are already known in various different forms, thus for example from WO 99/36623 or WO 03/016605.
The non-woven fabrics to be produced usually contain a mix of natural fibres, for example cellulose fibres of cotton or loosened wood cellulose which has already been treated mechanically and/or chemically (fluff pulp), synthetic matrix fibres such as for example polyester, polypropylene or viscose as well as synthetic binding fibres such as for example so-called bi-component fibres as well as for example as absorption agents so-called super-absorbent polymers in particle form (SAP) or fibre form (SAF). Bi-component fibres usually have a core melting at elevated temperatures (190-250° C.) of for example polypropylene (PP) or polyethyleneterephthalate (PET) which are enclosed by a sheath which melts at lower temperatures (140° C.) and which comprises for example polyethylene (PE), or are connected in another form (side-by-side, fibril type).
Non-woven fabrics of that kind are used for example as a semimanufactured article for the production of diapers and sanitary towels, absorbent inserts for the foodstuffs industry or for insulating material.
An important process step in the production of such a non-woven fabric is for the fibre mix to be deposited as uniformly as possible on an air-permeable transport or conveyor belt. That deposit operation is effected by means of a forming head in which the fibres are mixed. The deposit operation is assisted by a suction device (suction box) beneath the conveyor belt, with which the fibres are sucked through the air-permeable conveyor belt towards the conveyor belt. The fibre mixes which are deposited in an admittedly tangled but uniform form are transported on the conveyor belt in the form of a fibre bed for further processing in subsequent process steps, for example the effect of heat on the fibre bed, so that the polyethylene sheaths of the bi-component fibres fuse together and stick together. Treatment with latex can also be effected. In addition it is possible for a plurality of fibre bed layers to be deposited one upon the other in order in that way for example to produce a multi-layer non-woven fabric or also only a thicker non-woven fabric.
The range of variations in the products which can be produced with conventional apparatuses and processes is usually restricted by virtue of the fact that only given kinds of fibres or fibre lengths are to be processed therewith, so that the known processes and apparatuses cannot be used to produced non-woven fabrics which contain both relatively short fibres and also relatively long fibres, in one forming step. The state of the art includes installations in which the deposit of the short and long fibres takes place in succession (EP 1 299 588) or with a card (WO 03/086709). Disadvantages here are the increased level of machine complication and expenditure and the low weights in relation to surface area which can be achieved, if the fibres are provided by way of a carding process.
Therefore the object of the invention is to provide an apparatus and a process which have a greater range of variations in respect of the fibres to be processed and thus in respect of the products to be manufactured.